Horticultural reader Ed Hanson has emailed me with a query:
I have a log burner at home that I also burn coal on (a type of smokeless fuel actually). Can I use this stuff from the grate as a pot ash feed, or would I need to sift out the coal. I don't want to put anything on that would damage the soil.
I think I know the answer, and it's a no, but I am not quite sure why, other than the coal waste won't break down, and may contain chemicals that you wouldn't want in the soil - particularly if it's a form of smokeless fuel that's been treated.
Can anyone fill in the gaps in my knowledge on the science of coal dust?